Several well-known types of apparatus have been employed heretofore for successively feeding or transferring piece-parts having planar surfaces, and particularly such parts when of sheet configuration, from a magazine-loaded supply thereof at a dispensing station to a workholder or nest at a receiving or work station.
One type of such apparatus has comprised a cross-slide actuated feed member or finger that is adapted to initially contact an outer edge of each successive lowermost sheet of a magazine-confined stack thereof, and to thereafter laterally displace each such sheet through a sidewall slot formed in the magazine to a receiving or work station normally positioned in close proximity to the magazine. While such an apparatus generally is of simplified and inexpensive construction, it is often inapplicable for use in situations where the sheets to be transferred are very thin and/or of fragile material, such as of writing paper thickness and/or rigidity. This is true even when some form of guide rails or channels are employed to facilitate the lateral displacement of the sheets.
A second type of sheet stock transfer apparatus employed heretofore has included a vacuum pick-up assembly coupled to a rotary transfer mechanism, the latter typically comprising a planetary gear assembly. One form of this latter type of apparatus has employed two diametrically disposed vacuum cups that are simultaneously advanced between different points of an essentially triangular closed-loop path having inwardly bowed sides, with two of the verticies defining the locations of the dispensing and receiving stations. Such an apparatus is disclosed in M. J. M. Langen U.S. Pat. No. 3,937,458.
While this latter type of apparatus is normally applicable for use in transferring diverse types of sheet stock, regardless of the thickness and/or rigidity thereof, the aforementioned planetary gear assembly employed therein is quite complex, and does not allow for precisely controlled linear displacement of the vacuum cups as they approach and are withdrawn from either the dispensing or receiving stations. Such sequentially controlled linear displacements of a vacuum cup are often desired, if not required, when precise positioning of transferred sheet stock is required at the receiving station, and particularly when the extraction, transfer and placement operations are performed at relatively high repetitive speeds, such as in conjunction with successively aligned workholders on a rapidly indexed turret.
It is also often desirous that the linear displacements in question be co-linear so as to allow the sheet stock dispensing and receiving stations to be vertically aligned. This may often be of particular importance when space requirements are at a premium, such as when the transfer apparatus is but one of a plurality of closely spaced instrumentalities that perform a succession of work functions on a given piece part during the fabrication thereof.
There has thus been a need for an inexpensive, simplified and reliable sheet stock transfer apparatus that is applicable for use in handling diverse types of material sheets, regardless of the thickness and/or rigidity thereof, and wherein precisely controlled linear-to compound linear and rotational-to linear displacement is imparted to each successive sheet during the transfer operation.